Crankcase overpressure and blue smoke in the exhaust on a 2.5 AFB engine

Hello everyone,
"For the past 500 km, I've been experiencing burnt oil in the exhaust on my 2.5-liter AFB engine (110 kW, manufactured in October 1998, 147,000 km). I replaced the turbocharger 300 km ago with a brand new one and cleaned the entire turbocharging system. Unfortunately, the blue smoke is still coming out of the exhaust. I suspect that the crankcase ventilation system may not be functioning correctly. When I open the oil filler cap with the engine running, I can hear a distinct hissing sound and see oil mist escaping, indicating excessive pressure in the engine. I've now disconnected the crankcase ventilation system from the intake manifold and blocked it with verschandeln cloths. As a result, no oil is entering the intake manifold from the crankcase ventilation system." Could it be that the relatively high pressure in the crankcase during the "intake stroke" causes oil to bypass the oil scraper ring and enter the combustion chamber? At what pressure must the pressure relief valve open on the AFB? Is a pressure of 0.5-1 bar in the crankcase normal? Can the pressure regulating valve be replaced individually?
Thank you for your contributions!

Hi,
I can't imagine that a significant amount of overpressure is normal or desirable. Specifically, the various types of shaft seals are typically not designed for this.
My engine has such a strong vacuum that, when idling, no gases escape through the open oil filler cap.
Show a seasoned mechanic or car enthusiast what's coming out of your engine. If the amount is unusually high, it could be an indication of a serious problem (severe wear or a faulty piston ring).

Yes, the suspicion arises – perhaps a piston ring or something similar – but I actually have another theory, and I've also posted about this component in the forum, for example, at /viewtopic.php?t=1271&highlight=%F6lverbrauch.
"I've found it. I've now removed the entire oil filter module (which was a messy job) and I've determined that the overpressure is likely caused by the pre-filter, which is supposed to remove contaminants from the "air" before it reaches the oil, as it operates under pressure." Perhaps this component has other problems besides the leaf spring described in the link.

If you don't have the means to do it yourself, have the crankcase pressure measured. It only takes a few minutes. To do this, the measuring device is simply attached to the oil dipstick tube. The pressure must not be higher than 5 mbar; otherwise, the oil mist separator must be replaced. Generally, excessive pressure can also manifest as slight oil leakage around the cylinder head gaskets.

Best regards.

Hello,

According to the manufacturer's specifications for the first 2.5 V6 engines, the crankcase pressure should be checked every 60,000 km. The reason for this was apparently a faulty filter design that became clogged with oil sludge. Because my A4 2.5, manufactured in 2/98, was losing oil, I suspected the filter. Unfortunately, nothing changed after replacing it. In addition, the entire intake system was full of oil, which is why I disabled the EGR valve. However, my main concern is the turbocharger. You can't really expect a turbocharger in a budget-priced car like an Audi to last longer than 110,000 km under long-distance driving conditions, can you?

Thank you very much.
You're encouraging me.
The loader is already new, and the oil isn't coming from the intake manifold. But that filter was quite expensive.
Let's see what comes out. Keep me updated.

@der_marco

Hi, has your problem been resolved yet? I'm experiencing the exact same issue. My mechanic wants to do a complete engine replacement, which will cost over 10,000 euros. There must be another way to do this.
I also have an AFB (Annual Firearm Registration) from 8/99.

Sure, here's the translation:

'Hello' or 'Greetings'

v6Motion

How many miles are on your engine now?

Here's a private message from Marco, by the way.


'Thanks for the tip.'
It was a bullseye.
The oil separator was completely sealed.
'But this was the first time in the approximately 80,000 kilometers I've driven this car.'
Do I need to start including the cost of oil separators more frequently in my calculations?
Thank you again!

Sure, here's the translation:

'friendly' Regards,

Marco

As far as I know, this issue is common with the AFB, so please have your case pressure checked.

Best regards.

@ Marco:

How much goodwill did you show when you took over the company? I hope you installed the improved part from AKN.

Best regards.

@vikinger

KM: 91000

I had the same problem 2000 kilometers ago, and at that time, it was said that the cooling system was sealed. Then it was adjusted, and now we're having the same problem: the pressure in the main line is 270 mbar.
Compression pressure in all six cylinders below 19 bar.
They are now installing the oil separator from the 132kW model. Let's see if it works then. The engine has been tuned with a Cartronic Powerbox - that's why VW is not offering any warranty coverage - and a request for special warranty consideration was also denied.
A cost estimate of €10,100.00 is available.

Are there any other ideas, or should I get it repaired and sell it quickly?

Hi.

v6Motion

Did you happen to adjust the valves for some reason, perhaps after a timing belt failure, for example? In this case, a piston ring may have become stuck.
Is it possible to purchase the oil mist separator individually now? To my knowledge, the entire oil filter assembly is always replaced. How much does this replacement cost?

@vikinger

I'm not aware of any timing belt issues – since I've owned the car, there hasn't been any sign of it.
Regarding the cost, all I know is that the part is from Audi, as it's supposedly not available from VW, and it's supposed to cost €120.00.

Do you know any more details or a part number?

Yes, that's the right price range. Then the entire oil filter module will be replaced again (the filter holder with valve, etc., should be part number ET 059 115 405 D). However, the installation time is quite significant (requires putting the locking mechanism in a service position, removing the pump, removing the turbo, etc.). Well... Driving an Audi or a VW is definitely an expensive hobby (or maybe more of an expensive frustration ).

Best regards.

@Vikinger

Okay, great - I paid a total of €238.00, including the compression pressure test. I will probably have a pressure test done regardless, so that it's clear which piston is leaking where.

If the pistons are actually damaged, a new engine will be needed.
Do you have any idea if I can install the AKE (132kW) without making any major modifications?
'The control unit is available, and I can also get the entire engine - including...' Turbo, fuel injection system, etc.

Do you have experience with that, or would you prefer an AFB or AKN instead?

Sure, here is the translation of the text from German to English:

'Hello,'
v6Motion

As far as I know, the main difference lies in a different pump and different nozzles. I would definitely consider such a renovation to be within the realm of possibility.
Considering that my engine now has 70,000 kilometers on it, it's also just over three years old, and therefore all discussions about warranty coverage are likely over, I'm starting to feel anxious.